#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>


int main()
{
    pid_t id = fork();
    if(id < 0)
    {
        printf("errno : %d, errstring: %s\n", errno, strerror(errno));
        return errno;
    }
    else if(id == 0)
    {
        int cnt = 3;
        while(cnt)
        {
            printf("子进程运行中， pid: %d\n", getpid());
            cnt--;
            sleep(1);
        }
        //int*p = NULL;
        //*p = 1;
        exit(123);
    }
    else
    {
        sleep(20);
        int status = 0;
        pid_t rid = waitpid(id, &status, 0); // == wait
        if(rid > 0)
        {
            printf("wait sub process success, rid: %d, status code: %d, singal: %d\n", rid, status >> 8 & 0xFF, status & 0x0F );
        }
        else
        {
            perror("waitpid");
        }
        while(1)
        {
            printf("我是父进程: pid:%d\n", getpid());
            sleep(1);
        }
    }
   

    return 0;
}
